The Waitomo caves are a phenomenon unique to New Zealand: the walls and ceilings are covered in thousands of blue glowworms
Waitomo Glowworm Caves
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Eisriesenwelt Ice Cave
Nestled in the heart of the Tennen Mountains in Austria, the Eisriesenwelt is the largest ice cave in the world.
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Son Doong Cave
Son Doong, the largest cave in the world, only opened to the public in 2013. The vast expanse could house a 40-floor skyscraper with room to spare.
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Paris Catacombs
The Paris Catacombs hold the largest ossuary in the world. Beginning in the late 18th century.The Paris Catacombs lie 20 metres underground
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Wieliczka Salt Mine
The Wieliczka Salt Mine was operational for nearly 700 years, dug out of the entrails of the earth by generation upon generation of miners
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Derinkuyu Underground
A church, a school, a stable, even a prison—these are some of the impressive facilities found inside the underground city of Derinkuyu, in Turkey
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